Automatic punching machine



Sept. 26, 1967 w. OSTER 7 3,343,437

AUTOMATIC PUNCHING MACHINE Filed Jan. 18, 1965 STROKE CONTROL UNIT I INVENTOR.

WERNE R OSTER ATTORNEY United States Patent ABSTRACT OF THE DISCLOSURE An automatic punching machine in which the punch tool upon contact with the punch plate closes an electrical circuit to. control the length of the punch stroke. The plate has a plastic matrix with metal fibers distributed therethrough.

This invention relates generally to a punch press and, more particularly, to ,an improvement for automatically controlling the punch stroke in an automatic punching machine employed for cutting or stamping non-conducting materials, such as leather, textile or paper.

In devices of the type here under consideration, the punch proceeds on its down stroke into and through the workpieces until they are pierced and an actual contact is established with the punch plate and an electric circuit is caused to be closed and as a consequence thereof the punch is retracted. This construction necessitates a close control over the punch stroke and more particularly the terminal end thereof to avoid damage to the punch tool and plate. It is necessary to construct the punch plate of a material which is relatively softer than the punch tool. For this purpose aluminum has ben utilized. However, aluminum is still relatively hard and the cutting edges of the punch tool wear out rapidly and must be replaced or resharpened at an excessive rate. This has the effect that in addition to clostly precision grinding, the production capacity of the machine cannot be fully utilized. Moreover, the cutting edge of the punch cannot protrude sufiiciently into the aluminum plate and thus compensate for other portions of the cutting edge which are not exactly in the same plane. In these devices the tolerances must therefore be very closely observed. The control for the downward punch stroke must necessarily be set, so that the end of the stroke is not reached until all portions of the cutting edges have pierced the blank or work piece. Since the surface hardness of the aluminum leaves no margin for slight error or difference in tolerance, it is a frequent occurrence that lower lying cutting edges of the punch tool are bent and ruined.

It is therefore the primary object of this invention to provide an automatic punching machine overcoming the difliculties of the prior art.

It is another object of this invention to provide an automatic punching device having a punch plate which avoids damaging the cutting edges of the punch tool.

It is another object of this invention to provide an automatic punching device having a relatively resilient punch plate and incorporating therein a network for electrical conductance to close a control circuit when the cutting edge of the punch touches the plate.

One aspect of the present invention resides in the provision of an automatic punching machine, which includes a reciprocably disposed punch including cutting edges at least partly formed of conducting material. A punch plate is disposed for intermittent operating contact with the punch. The plate consists of a matrix of non-conducting material and conducting means, such as a mat of metallic fibers, which are distributed through the matrix and arranged for contact with the cutting edges of the punch. An electric control system, which includes an electrical connection to the cutting edge of the punch tool and a connection to the fiber mat of the plate is adapted to control the length of the downward stroke of the punch tool and its reversal.

For a better understanding of the present invention, together with other and further objects thereof, reference is had to the following description taken in connection with the accompanying drawings, and their scope will be pointed out in the appended claims.

In the drawings:

FIGURE 1 is a perspective view of a typical automatic punching machine;

FIGURE 2 is a fragmentary, enlarged, view of portions of the device herein under consideration, and includes a diagrammatic represenation of the electric control circuit.

Referring now to the drawing, there is shown an automatic punch press or machine 10 of generally conventional construction except as will hereinafter become more apparent.

So far as pertinent herein, the machine 10 includes a punch 12, also frequently referred to as a punch tool, rigidly mounted on a support 14. The support is arranged for reciprocatory movement the details of which do not form part of this invention. The punch 12 has cutting edges, e.g., 13, of tool steel or other appropriate electrically conducting material. The punch 12 faces a punch plate 16 upon which the work piece (not shown) is suitably mounted.

In the preferred embodiment, the plate 16 is composed if a matrix formed of a plastic material and distributed therethrough are a plurality of metallic, electrically conducting, discontinuous fibers which are mechanically interlocked forming a coherent network or mat 18. Alternatively, discrete fibers, constituting a fairly high percentage relative to the volume of the matrix material, may be utilized.

The punch plate 16 may be fabricated, using for the matrix material thermoplastic synthetic granules and embedding the mat of metal fibers 18 thereon. In this case the resulting mixture is heated and pressed to a degree and magnitude avoiding cavities. Alternatively, the mat 18 may be placed into a body of suitable plastic material in liquid form and thereafter the same is hardened in the conventional manner.

It should be noted, that inasmuch as the punch tool has usually different structural embodiments for any given task, it is desirable that the plate 16 be electrically conducting at practically all surface areas which may come in contact with the punch. This will of course in crease the versatility of the device.

An electric control system 20 provides the operating control over the upward and downward (punching) stroke of the punch 12. The system 20 is associated with a circuit having source of current 22 and a connection 24 to the cutting edge 13 of the punch tool 12. Another portion of the circuit, see 26, is suitably connected by solder or an intermediate electrode, not shown, to the mat of conducting fibers 18.

In the circuit, the fiber mat 18 of plate 16 thus functions as a stationary contact, while the cutting edge 13 is the moving contact. A coupling of the cutting edge 13 and the fiber mat 18 closes the circuit. The control unit 20 functions to terminate the downward stroke of the punch the instant that the circuit is closed. In other words, as soon as the punch has cut through the work piece, the control unit 20 is effective to cause the support mounted punch 12 to come to a halt and reverse its direction of movement.

While there have been described what are at present considered to be the preferred embodiments of this invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is, therefore, aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. In an electrically responsive automatic punching machine, comprising: a reciprocably disposed punch at least partly formed of conducting material; a punch plate disposed for intermittent operating contact with said punch, the punch plate comprising a matrix of non-conducting material having omnidirectionally oriented and uniformly distributed therethrough in substantially close physical contact insert means formed of conducting material arranged for contact with a conducting portion of said punch; and electric control means coupled to the conducting portions of said punch and said punch plate and effective for controlling the length of the punching stroke of said punch.

2. In an automatic punching machine according to claim 1, wherein said control means is effective to automatically terminate the punching stroke of said punch upon contact of the latter with said plate die.

3. In an electrically responsive automatic punching machine, comprising: a reciprocably disposed punch having an electrically conducting cutting edge; a punch plate disposed for intermittent operating contact with said punch, comprising a matrix of plastic material having uniformly distributed therethrough a metallic fiber mat arranged for electrical conducting contact with said cutting edge; and electric control means electrically connected to said cutting edge of said punch and said fiber mat and effective for automatically controlling the length of the punching stroke of said punch and for terminating said stroke upon electrical contact between said cutting edge and said fiber mat.

4. In an automatic punching machine according to claim 3, wherein said matrix is formed of pressed together thermoplastic granules and the fibers arranged therein are discontinuous and mechanically linked with each other.

References Cited UNITED STATES PATENTS 2,788,070 4/1957 Seabury et al. 83524 3,167,990 2/1965 Gilmartin 83658 3,178,976 4/1965 Kraut 83537 X WILLIAM W. DYER, JR., Primary Examiner.

WILLIAM S. LAWSON, JAMES M. MEISTER,

Examiners. 

1. IN AN ELECTRICALLY RESPONSIVE AUTOMATIC PUNCHING MACHINE, COMPRISING: A RECIPROCABLY DISPOSED PUNCH AT LEAST PARTLY FORMED OF CONDUCTING MATERIAL; A PUNCH PLATE DISPOSED FOR INTERMITTENT OPERATING CONTACT WITH SAID PUNCH, THE PUNCH PLATE COMPRISING A MATRIX OF NON-CONDUCTING MATERIAL HAVING OMNIDIRECTIONALLY ORIENTED AND UNIFORMLY DISTRIBUTED THERETHROUGH IN SUBSTANTIALLY CLOSE PHYSICAL CONTACT INSERT MEANS FORMED OF CONDUCTING MA- 